SUBORDER c PERISSODACTYLA 161 



Eocene ; North America. T. megarhinum Earle. According to Pilgrim, also 

 in Burma. 



Mesatirhinus and Mesarhhms Osborn. With narrow skull. Eocene. 



Dolichorhinus Osborn. Skull elongated, with long muzzle. Eocene. 



Diplacodon Marsh. Nasal bones short, often with two lateral bony- 

 protuberances. Extremities robust. Upper Eocene ; Uinta beds. 



Brachydiaste^nathermm Boeckh and Maty. Only lower jaw known. 

 Middle Eocene ; Transylvania. 



Subfamily 2. Titanotheriinae Osborn. 



2-0.1. 4. 3. 

 2-0.1.3(4).3. 



2-0.1. 4. 3. 

 Dental formula: ' ' ' • Dentition in a continuous series. Milk 



Fig. 218. 



Megacerops (Brontops) roiustus Marsh sp. Oligocene, Dakota. Restoration of skeleton, about 1/40- 



(After Marsh.) 



2.1.4. 



dentition: ^ • Incisors small, occurring in varying numbers, sometimes 



rudimentary or absent. Canines conical, generally small. Premolars and molars 

 similar. Naso-frontal border with a pair of well-developed obtuse bony prominences, 

 which in late members of this group may attain huge dimensions, as in Symborodon 

 and Brontotherium. Manus with four digits, pes tridactyl. Oligocene ; North 

 America. One very imperfectly preserved species, also, in Europe. 



These enormous animals have a height of nearly two and one-half metres, 

 and are only a little smaller than the elephant. Entire skeletons, numerous 

 skulls, and a great abundance of other remains have been found in the White 

 River beds (Lower Oligocene) of Nebraska, Dakota, and Colorado. 



Titanotherium Leidy (Palaeotherium Prout ; Menodus Pomel ; Brontotherium, 

 Menops Marsh) (Fig. 220), derived from Diplacodon ; Megacerops Leidy (Brontops 



VOL, III M 



